At present, many modern scientific instruments need accurate magnetic field circumstance for operation; in fields such as navigation, communication, magnetic levitation trains and medical applications, many equipments also function based on measurements of magnetic fields. In particular, magnetic field finds more applications in fields of electrical motors such as multi-degree-of-freedom motors and servo-motors.
A moving coil type magnetic levitation planar motor is a motor that functions based on a magnetic field circumstance generated by a magnetic steel array, and can realize long range motion by enlarging the area of the magnetic steel array. It has a large and particularly arranged magnetic steel array positioned on a stationary platform and has several sets of moving coils positioned on a moving platform and connected with a workbench. During the motion of the workbench, it is possible to determine the position of the workbench only by determining the positions of the moving coils.
In many motion systems including planar motors, high precision grating rulers are used as position detecting elements, which have high measurement accuracy but require complex circuits and optics, thus resulting in high cost. At the same time, there are also systems that directly utilize Hall sensors to measure positions. The patent PCT/IB01/02509 describes a system including magnetic steel arrays and moving coils, and relates to a direct use of Hall sensors for position measurements. However, noise exists in both the measured signals per se and the sampling process, which leads to a loss of measurement accuracy.